Method of producing metal articles with highly finished surfaces for coating



Patented Sept. 9, 1952 METHOD OF PRODUCING METAL ARTICLES WITH HIGHLY FINISHED summons FOR COATING -.Roland A. .Whitbeck, Lorain, Ilhio, assignorto Gilron Products company Cleveland, Ohio, a

corporation of Ohio :No Drawing.

.Thisinvention relates to a method of producing formedimetal ,articles for receiving highly finished surfacesforcoating and to metal articles havingthin hard; permanenthighfinishor gloss decorative and protectivesurfacecoatings such .as: surface coatings of bright nickel or chrome .plate or of quick dryinghigh-glosslacquers and thelikesuch as customarilyusedscn automobile bodies. p 1 A .This application is a continuationinpart of my .copending application.Serial No. 690,834, filedOctober 15, 1946,. now abandoned.

.In the automotive trade for example, automobile bumpershead lights, and other; parts are bright plated with an extremelythin coating of the plating materials. .Automobile bodies and the like .are coated "with verythin coatings of quick drying paints and enamelswhich usual- 1y include veryvolatile solvents.

Insuch instances, particularly in the case of bright plated'articles, since the coating is very thin 1 its outer exposed: surface conforms in contour to the metal surface on which it is applied and it does notbridge across. anyscratches or surface irregularities as do thick coatings. any scratches, blemishes or other surface irregularities on the metalsurface of the article are readily. discernible in the outer surface of the coating. Furthermore, due to the thinness of such coatings, if by chance a coating should bridge across any scratch or surface irregularity, the coating .soon breaks through leaving the metal therebeneath exposed. Likewise in the event of soiled or contaminated spots on the surface of the metal on which the coating is placed,

spots andthe portion of the coating overlying the soiled spots subsequently fiakesoff because of'lack of adherence and'because the coating on the metal adjacent thereto is too thin and weak tosustain that overlying the soiled spots. It is apparent'therefore that when so coating articles the surface of the metal to which the coating is applied must be very clean, polished, and free from any scratches, blemishes and contamination.

For thepurposes of illustration my method will be described as applied to the preparation and production of automobile bumpers having bright plated surfaces, the problems presented thereby and the solutions therefor, as applicable to other articles having bright plated surfaces, and articles ha ving thin high gloss coatings of enamel, lacquer, and the like, being readily apparent from the illustrative example.

Thus

35 the coating does not adhere properly to such Application November 1, 1949-, Serial No. 124,949 a 13.0]aims. (01. "113416) i In the production of. automobile bumipershav .ing bright plated surfaces, the prior1practicehas been as followst w M I The metal stock from which the bumpers are made isa very tough steel anddifficultto draw.

This stock as received from the steermiu is first blanked out, then heated 'and hot drawn to the desired shape and=contourafter which it is deep -pickledfora long period to remove gscale andforeign matter. .After deep-pickling it is rin'sedin hot water and .cleaned in a strong aqueous alkaline bath -which not only cleans the surfaceareas thereof which are relatively flat orhave asimple curvature of longradiusbeing rough polished by machines and the surface areas of shortradius and of compound curvatures and the less accessible areasbeing polished by hand. In these polishing steps compounds employing mixtures of abrasives and oils, greases or waxes areused. Afterpolishingthe surfaces they are hand buffed using 'conventional grease and waX-containing'bufling compounds. After buffingrthe'formed article iscleaned by soaking in a strong alkaline bath, followed by a water rinse. Next the article is electrolytically cleaned, rinsed, given a light acid rinse to make the'sur face receptive forthe platingbut not sufficient exposureto disturb the polished finish; It may then'be rinsed in water. Following rinsing the surfaces-are electroplated with copper, nickel and chrome, successively. Usually, in the first plating bath they are subjected to a reversal of currentforwaninstant in order to condition the surface.

After plating, the :.plated surfaces are buffed again to the final finish desired.

If thesurfaces are to be coated with enamel and'thedike, the article, after the cleaning effectedby soaking in the strong alkaline solution, and rinsing, above described, is dried andthe coated.

As" an example, assuming aplant to have a capacity of TLOOO-bumpers in twenty-four hours using thislmethod; most of the'time consumed in actual production thatrequired for the deep pickling, polishing and bufilng steps. A very substantialamount of time also is lost due to down .time for die touch-up and reconditioning. The'percentage of rejectsisirelativelyhigh.

Oneof the greatest diiiiculties encounteredin the prior :process islthat of 'properlyxandl uniformlyypolishing and bumng the surfaces of the One of the objects of the present invention I is to provide a method of producing formed articles with high gloss surfaces in which the.

difficulties encountered in the prior process are overcome and, concurrently, a number of the longest and most expensive steps of the prior process are eliminated.

Another object is to produce articles having a better and brighter finish than those produced by the prior method.

A more specific object is to provide a method of producing formed articles with bright plated or high gloss surfaces in which the surface to be coated is polished to the desired high degree of smoothness before the metal stock is formed and While it is flat, in which the polished surface is retained in the highly polished condition and free from scratches and contamination throughout the die forming operations, and in which the prior art step of deep pickling is eliminated.

In accordance with the present method, flat steel strip stock for automobile bumpers, as received from the mill," is dry polished in the flat'by machines employing sanding belts and abrasives, without oils and greases, to provide the surface desired, following which the stock is-washed in hot water to remove any abrasive grits.

Such a surface is obtained by the use of abrasive grits with a fineness of 200 mesh or more; for example, of 280 mesh. I

If in any instance polishing'compounds which include oils and greas'esare used,-the polishing can be done quite easily with the stock in the flat, but an expensive cleaning step must follow such practice and polishing without greases, oils, and waxes is much to be preferred.

The flat polished stock is then coated with a completely water-soluble composition which preferably comprises an organic lubricating and protective binder and a major portion of waterliberating and glass-forming inorganic material, and which is free from any'abrasive or barrier material. If desired, a small amount of organic hydrophilic collodial material may be included but such is not necessary.

The stock so coated is then-cold blanked in the absence of any other lubricant and, without recoating and in the absence of any other lubricant, is cold formed and drawn in dies to the desired final shape. After drawing, the formed article is cleaned in a mild alkaline bath often followed by Water rinse, this being the only cleaning necessary due to the complete water solubility of thecoating employed. If desired, this cleaning step may be followed by a short electrolytic cleaning as a precautionary step for the removal of any fingerprints, oils, greases and the like which may be on the surface as an incident of handling the articles but such is not necessary if care is exercised in handling after the water cleaning step. Again, after cleaning,

the article may be dipped in acid, if desired, to open up and superficially etch the surface. This acid dipping step is not to be confused with pickling in acid. The acid dipping step is of very short duration and merely assures clean ing and causesa very slight superficial surface action 01' etching which conditions the surface for better adherence without essentially changing its condition of smoothness. It is not the usual deep etch which requires an appreciable interval or a pickling step which requires long exposure of the metal to the acid and actually causesdissolution and freeing of scale and the like and very deep pitting of the surface, changing its condition of smoothness materially and rendering'it relatively rough. This step is optional, but is preferred. It is usually followed by. a watery rinse. The article then is plated, its surface being substantially in the polished condition in which it existed at the end of the original polishing operation and fr'ee from scratches, blemishes' die marks and the like. In case the article is to be coated with an enamel and the like, the rinsing step following the acid rinse is followed by drying.

The'usual steps of buffing, polishing or other steps of finishing the articles following, the plating or painting operationare unnecessary. The polishing stepabove described is preferably a dry polishing step using no coolant whatever. On very thin stock where the temperature of the stock may be raised an undesirable degree by the polishing, wateror completely water-soluble materials'may be used, as a coolant though this generally is unnecessary. s I

Since the protective and lubricating coating adheres tenaciously to a highly polished surface when dried thereon, it can be used withoutany danger of failure in providing proper lubrication during the forming operation. Thus the expensive steps of heating and hot forming-the stock, deep pickling, hot rinsing in a strong alkaline bath, hand polishing, buffing, cleaning in strong alkaline baths, and rebuffing, are eliminated. 7

As a comparison with'the example heretofore given as to the production obtained with the prior methods, 'a plant which :under the'prior method could produce about 7,000 bumpers'in twenty-four hours can, using the present method, produce 7,000 bumpers in eight hours. ,The saving in time in actually processing the stock is about one-third, and additional savings result from the elimination of down time for die retouching and regrinding, the substantial elimination of losses due to rejects, less'space requirements, and longer die life. The die life in the present method is practically unlimited as there does not appear to be any die deterioration.

By the use of the present method therefore, the stock is polished to the required high polish in the flat and formed without contamination of the surface and without scratching or marring the polished surface and the polished surface can be plated or otherwise coated in the'polished condition in which it exists at ,the completion of the forming operation. All that is necessary is to wash off the residual lubricating composition.

The composition used in the present method is one composed entirely of water-soluble materials. A dry mix of the ingredients of the composition is dissolved in waterin the ratio of about one pound of the dry mix to one gallon ofwater and is applied to the polished stock by dipping,

Broad Preferred A water-soluble organic lubricating andpro- Percent Percent -.tecting.binder 1 -33 Water-soluble inorganic glass-forming water i liberating material, such as alkaline earth J metal boraten. -90:67 80 One class of materials which may be used as ,the organic lubricating binders 1are.water soluble soaps,preferably {high titre soaps, having :amelt- Ling point of a least about 36 centigradegup wardly, specific examples being tallow soap, palm oil soap, stearic acid soap, cocoa butter soap, Borneo tallow soap, hydrogenated :tallow-soap, coaceric. .soap, iapanic .soap, .palmitic acid :soap,

stearin flux soap, multiple pressed tallow-;soap,.

hydrogenated palmoil soap, and multiple-pressed palm oil soap.

It should be noted thatreachof the above soaps may be used individually or in admixture with one or more of the other soaps.in;any=;.desired proportions, in so long as the amount ofw'so'ap present is within the broad limits hereinbefore recited.

An additional class ,of materials are watersoluble aliphatic polyhyldric alcohols .haVihgIless j than four hydroxy groupsiatty acides'ters thereof orrmixturfesof either, or both, ,and withaparticular preference .for those having a melting point of .at least about 40 centigrade, specific examples being polyethylene glycol, polyethylene glycol oleate, glyceryl stearate, propyl ne glycol stearate, di-glycol stearate, et c. I

As hereinbefore indicated, mixtures of compounds in each class arecontemplated forusepin blendin the ultimate composition. Moreover, it

should be particularly stated that a mixture of the two aforementioned classes may be employed, such as, for example, a soap and a polyhydric alcohol, soap and an ester of the alcohoL'a mixture of soaps and analcohol or anester or a,

mixture of the two. When employing such a mixture the soap should always 'bein;the same or greater amount as the .polyhydric alcohol.

"The water-soluble alkaline earthjnetalborates employed in combination With the organic lubricating binder include borax, lithium borate,

and potassium borate; Borax is the preferred 'material dueto its ready availability and low cost and-also, in certain methods of-applicatiojn, the other borates tend to disburse theorganic binder'and, if the coated-metal stockstands for any considerable periodof time;the 'coatingtends to become tacky. I

In some instances, it will he found beneficial to combine with the aforesaid composition a minor amount of an organicjhydrophilic'colloidal material such as, for examplefcornstarch, potato starch, wheat starch, 'etc. Under such circumstances the colloidal material will be -present' in an amount frombetweenabout1%-'to8'%, the lubricating binder about 15% to%, and the b'orate about 67% to 84%.

Having described the compositiomtob eem- V convenient to list a few illustrative examples of 6 such compositions, ,the percentages given being byweight:

Example 1 (Ifallow soap ca Borax Example? Palm oil soap Q.-. 18 Borax PM"a-.- 21132 "Example 3 I, Tallow soap V Q 24 Borax 76 Ewampled 1 Tallow soap -f Palm oil soap Borax y; 84:

Examplej .Palm oil soap Borax Example .6 s

Polyethylene glycol w ur 15 Borax 85 Emampleji'j j Polyethylene .glycols. t Manama, i922 Borax 78 Example 8 Polyethylene glycol Polyethylene glycol oleate -i Borax Emampley V Polyethylene glycol oleate 7 Lithium borate 93 Example '10 I Polyethylene ..glycolrnmflmnvflWhamL28 Potassium borate 72 Example 11 "Glyceryl monostearate p Polyethylene glycololeate 12 Potassium boratel 8 8 'ExampZeIZ I Propylene glycol stearate, Lithium borate H '70 i 'EwampZe 13 g Diglycol stearate 18 Borax -Q 82 i I i m -4 iPropylene.glycolstearate.. 5 a

Diglycol stearate 20 Lithium borate V Exampleli f l Polyethylene glycohstearate 3 15 Propylene glycol stearate Borax 5 Example 16 Tallow soap 5 Polyethylene glycol 21? 0 Borax 3 5 Exemplar? Borax Glyceryl monostearate Polyethylene glycol oleate Potassium borate 75 Borax Example 22 Hydrogenated tallow soap '7 Propylene glycol stearate 25 Lithium borate 70 i Example 23 Coaceric Diglycol stearate 8 Propylene glycol stearate Lithium borate} 82 Borax Example 24 Palmitic acid soap Diglycol stearate 5 Borax 30 Example 25 Stearin flux soap .Borax 80 Example 26 Hydrogenated tallow soap 35 Borax 65 Example 27 Hydrogenated palm oil soap 10 Lithium borate 90 Example 28 Triple-pressed tallow soap Hydrogenated palm oil soap Potassium borate '70 Example 29 Cocoa butter soap 18 Potassium borate 82 Example 30 "Stearin flux soap 15 Lithium borate 85 Example 31 ('foaceric soap Borax '75 Example 32 Japanic soap 22 Potassium borate} Example 33 v. v Parts Borneo tallow soap 20 Boraxv Lithium borate Example 34 Stearate acid soap 28 Borax 72 Example 35 V Stearin flux soap l5 Stearic acid soap Borax Lithium borate Example 36 Borneo tallow soap 20 Triple-pressed palm oil soap Borax 80 Example 37 'Stearin flux soap 1'7 Borax 80 Sulphonated castor oil 3 Example 38 Hydrogenated tallow soap 22 Borax Lithium borate} 73 Liquid glycol If 5 Sodium lauryl sulphate I claim:

1. The method of producing, by drawing between metal dies, pressure shaped metal articles having highly polished surfaces for receiving a thin permanent high gloss decorative coating comprising: polishing the surface of metal stock, having the metallurgical properties required in the finished article, in the fiat with material of which the abrasive consists of grits of at least about 200 mesh fineness to the final highly polished finish required on the final article, cleaning the surface of the stock to remove the polishing material, then coating the polished surface of the stock with a composition of completely water soluble organic lubricating material and water soluble inorganic Water liberating metal salt, by applying and drying on the stock an aqueous solution of the composition to form on the stock a thin water soluble self-adherent and tenacious dry lubricating V and protective coating free from abrasive and barrier material and which, during the drawing of the stock'between the metal dies, is capable of lubricating and maintaining the polished surface, in the absence of the addition of other types of lubricants, in substantially the polished condition in which it existed at the completion of the polishing operation, then cold drawing the coated stock between metal dies, and washing off the residual coating material remaining on the shaped stock, whereby the polished surface of the shaped stock is substantially in the condition of smoothness in which it existed at the completion of the polishing operation.

2. The method of producing, by drawing between metal dies, pressure shaped metal articles having highly polished surfaces for receiving a thin permanent high glOSs decorative coating comprising: polishing the surface of metal stock, having the metallurgical properties required in the finished article, in the flat with material of which the abrasive consists of grits of at least 9 about 200 mesh fineness to the final highly polished finish required on the final article, cleaning the surface of the stock to remove the polishing material, then coating the polished surface of the stock with a composition comprising water soluble organic lubricating material and a larger amount of water soluble inorganic water liberating metal salt by applying and drying on the stock an aqueous solution of the composition to form on the polished surface a thin soluble self-adherent and tenacious dry lubricating and protective coating free from abrasive and barrier material and which, during the drawing of the stock between metal dies, is capable of lubricating and maintaining the polished surface, in the absence of the addition of other types of lubricants, in substantially the polished condition in which it existed at the completion of the polishing operation, then cold drawing the coated stock between metal dies, and washing off the residual coating material remaining on the shaped stock, whereby the polished surface of the shaped stock is substantially in the condition of smoothness in which it existed at the completion of the polishing operation.

3. The method of producing, by drawing between metal dies, pressure shaped metal articles having highly polished surfaces for receiving a thin permanent high gloss decorative coating comprising: polishing the surface of metal stock, having the metallurgical properties required in the finished article, in the flat with material of which the abrasive consists of grits of at least about 200 mesh fineness to the final highly polished finish required on the final article, cleaning the surface of the stock to remove the polishing material, then coating the polished surface of the stock by applying and drying on the stock, to form on the stock a thin soluble self-adherent and tenacious dry lubricating and protective coating, an aqueous solution of a composition comprising, by weight, water-soluble organic lubricating and protecting material about 10-33% and water-soluble, water-liberating inorganic metal salt about 90-67%, then cold drawing the coated stock between metal dies, and washing off the residual coating material remaining on the shaped stock, whereby the polished surface of the shaped stock is substantially in the condition of smoothness in which it existed at the completion of the polishing operation.

4. The method according to claim 2 characterized in that the metal salt is an alkali metal borate.

5. The method according to claim 2 characterized in that the Organic lubricating material is water soluble aliphatic polyhydric alcohols having less than four hydroxy groups.

6. The method according to claim 2 characterized in that the water soluble organic lubricating material is fatty acid esters of aliphatic polyhydric alcohols having less than four hydroxy groups.

7. The method according to claim 2 characterized in that the water soluble organic lubricating material is a mixture of polyhydric alcohols having less than four hydroxy groups and fatty acid esters thereof.

8. The method according to claim 2 characterized in that the water soluble organic lubricating and protecting material is a soap, and the water soluble inorganic metal salt is an alkali metal borate.

9. The method according to claim 2 characterized in that the polishing step is a dry polishing step.

1 The method according to claim 2 characterized in that, after removal of the residues of the lubricating coating, the article is subjected to an acid dip for a short interval of time and is then rinsed.

11. The method according to claim 2 characterized in that the water soluble organic lubricating material is high titre soap having a melt ing point of at least about 36 C., and the water soluble salt is borax.

12. The method according to claim 1 characterized in that a very thin high gloss decorative coating is applied to the polished surface of the shaped article.

13. The method according to claim 2 characterized in that a very thin permanent high gloss decorative coating is applied to the polished surface of the shaped article.

ROLAND A. WHITBECK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 23,184 Whitbeck Dec. 20, 1949 154,130 Eggleston Aug. 18, 1874 1,728,622 Mascuch Sept. 17, 1929 1,769,577 Hopkins July 1, 1930 1,952,973 Craig Mar. 27, 1934 1,977,448 Lyon Oct. 16, 1934 2,074,224 Johnson Mar. 16, 1937 2,120,461 Copeman June 14, v1938 2,126,128 Montgomery Aug, 9, 1938 2,133,445 Guerin Oct. 18, 1938 2,145,252 Engle Jan. 31, 1939 2,173,092 Baker Sept. 19, 1939 2,399,775 Whistler May 7, 1946 2,422,883 Bruderlln June 24, 1947 2,512,161 Ledel June 20, 1950 

1. THE METHOD OF PRODUCING, BY DRAWING BETWEEN METAL DIES, PRESSURE SHAPED METAL ARTICLES HAVING HIGHLY POLISHED SURFACES FOR RECEIVING A THIN PERMANENT HIGH GLOSS DECORATIVE COATING COMPRISING: POLISHING THE SURFACE OF METAL STOCK, HAVING THE METALLURGICAL PROPERTIES REQUIRED IN THE FINISHED ARTICLE, IN THE FLAT WITH MATERIAL OF WHICH THE ABRASIVE CONSISTS OF GRITS OF AT LEAST ABOUT 200 MESH FINENESS TO THE FINAL HIGHLY POLISHED FINISH REQUIRED ON THE FINAL ARTICLE, CLEANING THE SURFACE OF THE STOCK TO REMOVE THE POLISHING MATERIAL, THEN COATING THE POLISHED SURFACE OF THE STOCK WITH A COMPOSITION OF COMPLETELY WATER SOLUBLE ORGANIC LUBRICATING MATERIAL AND WATER SOLUBLE INORGANIC WATER LIBERATING METAL SALT, BY APPLYING AND DRYING ON THE STOCK AN AQUEOUS SOLUTION OF THE COMPOSITION TO FORM ON THE STOCK A THIN WATER SOLUBLE SELF-ADHERENT AND TENACIOUS DRY LUBRICATING AND PROTECTIVE COATING FREE FROM ABRASIVE AND BARRIER MATERIAL AND WHICH, DURING THE DRAWING OF THE STOCK BETWEEN THE METAL DIES, IS CAPABLE OF LUBRICATING AND MAINTAINING THE POLISHED SURFACE, IN THE ABSENCE OF THE ADDITION OF OTHER TYPES OF LUBRICANTS, IN SUBSTANTIALLY THE POLISHED CONDITION IN WHICH IT EXISTED AT THE COMPLETION OF THE POLISHING OPERATION, THEN COLD AND DRAWING THE COATED STOCK BETWEEN METAL DIES, AND WASHING OFF THE RESIDUAL COATING MATERIAL REMAINING ON THE SHAPED STOCK, WHEREBY THE POLISHED SURFACE OF THE SHAPED STOCK IS SUBSTANTIALLY IN THE CONDITION OF SMOOTHNESS IN WHICH IT EXISTED AT THE COMPLETION OF THE POLISHING OPERATION. 